In order to carry out processing such as grinding and etching on semiconductor wafers, it is necessary to temporarily bond semiconductor wafers, and various methods for doing so have been proposed. For example, at present, a method wherein a semiconductor wafer is bonded on top of a film for bonding that is a PET film whereon an adhesive layer has been provided is often used.
With this method, if the grinding precision (approximately 1 μm) of a back grinding machine generally used for grinding, and the thickness precision (approximately 5 μm) of a BG (back grind) tape generally used to fix a wafer are put together, the required thickness precision is exceeded, and there is the danger that variability in the thicknesses of the ground wafers may arise.
Additionally, when processing wafers used for through-silicon vias (TSVs), the formation of via holes and films is carried out in a state with a BG tape attached, but in these cases the temperature reaches approximately 150 degrees Celsius, and this unfortunately raises the adhesion of the BG tape. Additionally, the adhesive layer of the BG tape can be eroded by plating chemicals for film formation, and peeling can thereby occur.
Additionally, fragile wafers such as those in compound semiconductors may, in some cases, be damaged by mechanical grinding, so they are made thinner by etching. During this etching, there are typically no problems if the amount of etching is such that the aim is merely stress removal, but in cases where several microns worth of etching is done, the BG tape may be deteriorated by the etching chemicals.
On the other hand, a method has come to be utilized where bonding to a supporting substrate having a smooth surface is done, via a bonding adhesive. For example, when etching with the aim of stress removal, heating to a high temperature is necessary, but a PET film cannot withstand such a high temperature, so in such cases, a method using a supporting substrate is preferably utilized.
As the material for bonding to the supporting substrate, bonding materials that soften under high temperatures and thereby make the detachment of the wafer easy, and bonding materials that are dissolved by specific chemicals have been proposed.
However, the handling of such materials is poor, and after detachment, it is necessary to wash residual bonding material that has remained in the interior portions of the semiconductor wafer or device using chemicals or the like.
Additionally, when detaching the semiconductor wafer from the supporting substrate, there is the danger that the thinned wafer cannot withstand this and it breaks. As semiconductor wafers grow ever thinner, this probability can be expected to increase.
For example, Patent Documents 1 and 2 disclose polymers concerning the manufacture of a semiconductor device, although their aims differ from that of the present invention.
As described above, with regard to bonding in order to process a semiconductor wafer, a temporary bonding material was desired for which high precision processing is possible, it is easily detachable, and it does not readily remain on a semiconductor wafer.
Additionally, a manufacturing method for a semiconductor device that reduces the damage to semiconductor wafers, makes high precision processing possible, and can shorten the time needed for thermal decomposition was desired.